1.\" $OpenBSD: pthread_once.3,v 1.10 2002/05/01 08:03:30 mpech Exp $ 2.\" 3.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by John Birrell. 17.\" 4. Neither the name of the author nor the names of any co-contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.\" $FreeBSD: pthread_once.3,v 1.5 1999/08/28 00:03:09 peter Exp $ 34.\" 35.Dd April 4, 1996 36.Dt PTHREAD_ONCE 3 37.Os 38.Sh NAME 39.Nm pthread_once 40.Nd dynamic package initialization 41.Sh SYNOPSIS 42.Fd #include <pthread.h> 43.Pp 44.Ft pthread_once_t 45.Fa once_control 46\&= 47.Dv PTHREAD_ONCE_INIT ; 48.Pp 49.Ft int 50.Fn pthread_once "pthread_once_t *once_control" "void (*init_routine)(void)" 51.Sh DESCRIPTION 52The first call to 53.Fn pthread_once 54by any thread in a process, with a given 55.Fa once_control , 56will call the 57.Fn init_routine 58with no arguments. 59Subsequent calls to 60.Fn pthread_once 61with the same 62.Fa once_control 63will not call the 64.Fn init_routine . 65On return from 66.Fn pthread_once , 67it is guaranteed that 68.Fn init_routine 69has completed. 70The 71.Fa once_control 72parameter is used to determine whether the associated initialization 73routine has been called. 74.Pp 75The function 76.Fn pthread_once 77is not a cancellation point. 78However, if 79.Fn init_routine 80is a cancellation point and is cancelled, the effect on 81.Fa once_control is as if 82.Fn pthread_once 83was never called. 84.Pp 85The constant 86.Dv PTHREAD_ONCE_INIT 87is defined by header 88.Aq Pa pthread.h . 89.Pp 90The behavior of 91.Fn pthread_once 92is undefined if 93.Fa once_control 94has automatic storage duration or is not initialized by 95.Dv PTHREAD_ONCE_INIT . 96.Sh RETURN VALUES 97If successful, the 98.Fn pthread_once 99function will return zero. 100Otherwise an error number will be returned to indicate the error. 101.Sh ERRORS 102None. 103.Sh STANDARDS 104.Fn pthread_once 105conforms to 106.St -p1003.1-96 . 107